In the field of cardiac magnetic resonance imaging (“MRI”), various types of studies utilize multiple images along different “slice” planes to analyze the target of the MRI. This is particularly true with cardiac MRI techniques that can be used to map cardiac regions, such as cardiac cine examinations, perfusion, delayed enhancement, magnetization tagging, etc. Images are taken of planes along both a long-axis and a short-axis of the heart. The “long axis” is a plane parallel to the longest dimension of a target anatomical structure. The “short axis” is a plane parallel to the shortest dimension of a target anatomical structure. Conventionally, in cardiac imaging, it is desirable to acquire images in the long-axis plane in a uniformly angularly-spaced radial fashion to encompass the region imaged in the short-axis slices. Also, the frequency-encoding direction of the long-axis slices are taken “down the barrel” of the heart, i.e., normal to the image plane of the short-axis images.
One limitation of existing systems and methods is their inability to easily prescribe slice planes for capturing multiple images along an axis. For example, quantitative and qualitative cardiac MRI studies utilizing magnetization tagging have become important components of the cardiac MRI examination. When performing quasi-3D tagging studies, conventional procedures obtain a number of tagged images in the short-axis plane of the heart, with two orthogonal sets of tags, and combine these with tagged images obtained in the long-axis plane of the heart. Conventional techniques manually prescribe the long-axis slices.
In conventional graphical slice prescription techniques, a user defines a slice-selection (“SS”) direction, a phase encoding (“PE”) direction and a readout (or “frequency encoding” “RO”) direction are calculated based on the SS direction. RO is defined by the cross-product of the SS and PE directions, because the RO direction is normal to both the SS and PE directions. For example, let s, c and t represent sagittal, coronal, and transverse directions, respectively, and {right arrow over (P)}0:(Ps, Pc, Pt)), {right arrow over (R)}0: (Rs, Rc, Rt) and {right arrow over (S)}0: (Ss, Sc, St) represent vectors in the PE, RO, and SS directions, respectively, for a first long-axis imaging slice. Using this representation, and depending on the orientation of {right arrow over (S)}0, the PE vector can be provided as follows:{right arrow over (P)}0|t=[0,St/Kct,−Sc/Kct]{right arrow over (P)}0|c=[Sc/Ksc,−Ss/Ksc,0]{right arrow over (P)}0|s=[−Sc/Ksc,Ss/Ksc,0],where Kij=√{square root over (Si2+Sj2)} and the suffixes to {right arrow over (P)}0 indicate the direction of the SS vector. {right arrow over (R)}0 is then calculated by computing the vector cross-product, {right arrow over (R)}0={right arrow over (S)}0×{right arrow over (P)}0.
Conventional systems and methods are limited in their capabilities to provide a simple approach to developing quick radial prescription of long-axis imaging slices. Conventional systems require their users to manually prescribe the long-axis planes needed to develop these radial prescriptions. An examination typically consists of 8-10 slices which should be uniformly angularly spaced. As a result, manual prescription of long-axis slices can be a tedious process, and prone to error.